Japanese Non-examined Patent Publication No. 2000-340087 discloses a conventional contact device. The conventional contact device comprises a fixed contact; a movable contact coming into contact with and separating from the fixed contact; a movable plate carrying the movable contact; a drive mechanism which drives the movable plate to make the contacting engagement of the movable contact with the fixed contact; and a housing which houses the fixed contact, the movable plate, and the drive mechanism. The movable plate is a Z shape having a contact member carrying the movable contact on its one surface, a leg upstanding from the contact member, and a supporting member which is coupled at its one end to the leg and is fixed at the other end to the drive mechanism. When the drive mechanism is energized, the movable plate moves downward to bring the movable contact into contact with the fixed contact.
In this kind of contact device, when the movable plate overtravels after the movable contact came into contact with the fixed contact, the supporting member is deformed, which gives a contact pressure to the contacts. As shown in FIG. 12A, the contact pressure is a resultant force F of two forces F1 and F2; the force F1 is a force applied to the movable contact 100 by the movable plate 120 along a moving direction of the movable contact 100 for bringing the movable contact 100 into contact with the fixed contact 110 (downward direction in FIG. 12A), and the force F2 is a force applied to the movable contact 100 by deformation of the supporting member 120a through the leg 120b. The force F2 intends to open the leg 120 outward. Therefore, in this conventional contact device shown in FIG. 12A, a component force F3 parallel to a contact surface defined between the movable contact 100 and the fixed contact 110 is generated from the resultant force F, so, as shown in FIG. 12B, the leg 120b may pivot about its upper end S, and the movable contact 100 may slip sideways with respect to the fixed contact 110. Such side slip may cause a decrease of the contact pressure between the movable contact 100 and the fixed contact 110, which may increase a contact bounce time, and may cause contact weld, a breaking defect caused by an increase in transfer of a contact material, and a malfunction.